1. Field of the Invention
This invention relates to a lever type connector in which coupling and detaching of the connector are effected by a cam action and more particularly to a lever type connector which has a single kind of terminal or different terminals which have the same or different timing of insertion and extraction of the connector.
2. Statement of the Prior Art
Such a kind of connector has the advantage of enabling a coupling and detaching operation by a small force and is applied to a multiple (more than twenty) electrode connector. The connector utilizes a "lever action" as a basic principle and is known by, for example, the Japanese Patent Public Disclosure No. 4-62772 (1992).
For convenience of explanation, a prior lever type connector will be explained by referring to FIGS. 10 to 12.
FIGS. 10A to 10B are side elevational views of a prior lever type connector, illustrating each of the coupling steps. FIGS. 11A and 11B are vector diagrams which illustrate a "lever action" in the prior lever type connector. FIG. 12 is a side elevational view of a prior lever, illustrating a shape of a cam groove.
As shown in FIGS. 10A to 10D and FIG. 12, a female connector housing 1 accommodating female terminals is disposed over a male connector housing 2 accommodating male terminals. The female connector housing 1 is adapted to be inserted into the male connector housing 2. A lever 4 having a cam groove 3 which effects the "lever action" is rotatably attached to the male connector housing 2. A cover 5 to be put on the female connector housing 1 is provided with a cam follower boss 6. As shown in FIG. 12, the cam groove 3 in the lever 4 is formed in a circular arc around a bearing bore 4a which is a rotation center of the lever 4. Opposite side end faces 3a and 3b in the cam groove 3 serve as cam faces.
As shown in FIG. 10B, when coupling both connector housings 1 and 2, the cam follower boss 6 on the cover 5 attached to the female connector housing 1 is inserted into the cam groove 3 in the lever 4 and then the lever 4 is turned in an anticlockwise direction shown by an arrow. As shown in FIG. 10C, the upper side end face 3a pushes down the cam follower boss 6 so that the cover 5 is pushed down and the terminals in both connector housings are deeply interconnected and then the female connector housing 1 is inserted into the male connector housing 2. When the lever 4 is turned to a position shown in FIG. 10D, the female connector housing 1 is completely inserted into the male connector housing 2 and the terminals in both housings are completely interconnected.
In the coupling process of the connector as the female and male terminals are interconnected, a strong insertion resistance acts on the female connector housing 1. However, since an insertion force which overcomes an insertion resistance caused by the lever action between the side end face 3a in the cam groove 3 and the cam follower boss 6 acts on the female connector housing 1, it is possible to insert the female connector housing 1 into the male connector housing 2 by a relatively light force.
On the contrary, when the connector is detached from the position shown in FIGS. 10D to the position shown in FIGS. 10A, the lever 4 is turned in the clockwise direction. Since the lower side end 3b in the cam groove 3 pushes up the cam follower boss 6, the female connector housing is extracted out of the male connector housing 1 against an extracting resistance caused by a frictional force between the female and male terminals.
Generally, as shown in FIGS. 11A and 11B, it is possible in this construction to make a vertical force f.sub.1 acting on the cam follower boss 6 larger as an angle .theta. becomes smaller when .theta. in an angle between a horizontal line h and a line tangent to the cam face 3a at a point P contacting between the cam follower boss 6 and the cam face 3a in the cam groove 3. This will be apparent from comparison of vectors f.sub.1 and f.sub.2 in FIGS. 11A and 11B. Here, the vectors f.sub.1 and f.sub.2 are vertical and horizontal components of a force F acting on the cam follower boss 6. This means that the force acting on the cam follower boss 6 in connection with a rotation of the lever 4 depends upon a continuous change of the tangential line t on the cam face 3a, namely a curved line of the cam groove 3 in the lever type connector.
It will be understood from the coupling and detaching operation of the connector shown in FIGS. 10A to 10B that the right side end 3a in the cam groove 3 gives the cam action to the boss upon coupling of the connector and the left side end 3b in the cam groove 3 gives the cam action to the boss upon detaching of the connector as shown in an enlarged scale in FIG. 12.
On the other hand, when the insertion and extraction of the female and male terminals are carefully examined, changes in the respective resistances are observed to be different. That is, a curved line indicating a change of an insertion resistance upon insertion of the female and male terminals forms a peak when the female connector housing 1 is disposed in a shallow position in the male connector housing 2 since a larger insertion resistance is generated at a primary insertion of the terminals. Upon extraction of the terminals a larger extraction resistance is generated at a primary extraction of the terminals on account of a large stationary frictional force. A curved line indicating a change in the extraction resistance becomes a peak when the female connector housing 1 is disposed in a deep position in the male connector housing 2. This will be explained in more detail hereinafter.
However, since a width of the cam groove 3 in the prior lever type connector is substantially constant and thus the side ends 3a and 3b which serve as cam faces are set to be the same as each other, this construction does not exhibit the "lever action" effectively. That is, since the shape of the prior cam groove is designed to exhibit an even effect in coupling and detaching operations, for example, a sufficient insertion force can not be obtained under inserting terminals upon coupling the connector while a sufficient extraction force can not be obtained when initially extracting terminals upon detaching the connector. This means that a large actuating force must be applied to the lever and the lever must be a large size.
On the other hand, recently, a connector has been developed which has, for example, two kinds of terminals provided for an electrical power source supply and a signal transmission in a single connector housing. In this connector, generally, the terminals for the electrical power supply are of a large size while the terminals for the signal transmission are of a small size. When coupling the connector, the large terminals for the electrical power supply begin to interconnect and then the small terminals for the signal transmission begin to interconnect. Consequently changes in resistance upon insertion and extraction in connection with a turning operation of the lever 4 become a simple curve with a peak in the prior connector having a single kind of terminal and become a complex curve with two peaks in the connector having two kinds of terminals. This will be described in more detail hereinafter.
However, since the cam groove 3 in the lever 4 in the prior connector is formed into a simple circular arc as shown in FIG. 12, it is impossible to cause a force suitable for a change of insertion resistance to act on the female connector housing 1 and to operate the lever by a smooth and light force.